The use of oils or emulsifier/oil mixtures as herbicide adjuvants is a well-established practice in agriculture for improvement of post-emergence weed control applications through better coverage and penetration of the active ingredient on the leaf surface of the target weed. However, in pre-emergence applications these well-known effects cannot operate since the herbicide composition is applied directly to the soil, and the foliage of the target weed has not yet developed. Thus, it had been widely accepted that oil-based adjuvants would not have any beneficial effect on herbicide activity in soil-applied applications. There have been sporadic reports of activity enhancement of soil-applied herbicides in the literature. Generally these references deal with controlled release polymer-based compositions that reduce leaching and hold the herbicide in the soil surface. While these techniques tend to increase the activity of the herbicide after a prolonged period, frequently the initial weed control is unsatisfactory due to insufficient early release of the active ingredient.